feat: add expo mobile application source code

mobile/components/hello-wave.tsx

@@ -0,0 +1,18 @@
+import React from 'react';
+import { StyleSheet, Text, View } from 'react-native';
+
+export function HelloWave() {
+  return (
+    <View>
+      <Text style={styles.text}>👋</Text>
+    </View>
+  );
+}
+
+const styles = StyleSheet.create({
+  text: {
+    fontSize: 28,
+    lineHeight: 32,
+    marginTop: -6,
+  },
+});